<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>force-update</title>
  <script src="../../../vue.js"></script>
</head>
<body>
  <div id="root">
    {{x}}
    <child></child>
  </div>
  <script>
    let template = `
      <div v-once>
        child
        {{title}}
      </div>
    `

    Vue.component('child', {
      template,
      data() {
        return {
          title: 'hello'
        }
      },
      mounted() {
        this.title = 'world'
      }
    })

    var vm = new Vue({
      el: '#root',
      data: {
        x: ['a']
      },
      mounted() {
        this.x[0] = 'aaa'
        this.$forceUpdate()
      },
    })
  </script>
</body>
</html>